Membrane surface structures play an important role in the morphology and differentiation of cells. The carbohydrate moiety of glycoconjugates, glycoproteins and glycolipids, have frequently been found to be responsible for these biological properties. Thus, simple carbohydrate residues can affect the integrity of tissues, metastasis of tumors, the homing of cells in embryological development and other cellular interactions, e.g. between mannalian cells and bacteria or viruses. It might be concluded, therefore, that glycoconjugates behave as "Recognition Sites." We have recently demonstrated that such Recognition Sites play an important role also in hematology, e.g. the role of sialic acid in the viability of erythrocytes in circulation. Our objective, therefore, is to ascertain the mechanisms, and to identify the glycoconjugate(s) involved. To that end we intend to crack the carbohydrate code by using techniques developed in our lab such as the beta-elimination reductive cleavage procedure and the use of the alpha-N-acetylgalactosaminyl-oligosaccharidase.